As circuits on die scale with Moore's law, which predicts the number of transistors in a chip to double in about every two years, the passives such as inductors (also referred to as coils or reactors) used by products employing Voltage Regulators (VRs) similarly need to scale in tandem. An inductor is a passive two-terminal component which resists changes in electric current passing through it. When an electric current flows through the inductor, energy is temporarily stored in a magnetic field in the inductor. As the electric current through the inductor changes, the time-varying magnetic field induces a voltage in the inductor which opposes the change in current that created it.
The scaling of the inductors reduces the quality factor of the inductors, leading to efficiency loss. The quality factor (or Q factor) of an inductor is the ratio of its inductive reactance to its resistance at a given frequency, and is a measure of its efficiency. The series resistance of an inductor converts electric current through its coils into heat, thus causing a loss of inductive quality.
The term “scaling” generally refers to converting a design (schematic and layout) from one process technology to another process technology and subsequently being reduced in layout area. The term “scaling” generally also refers to downsizing layout and devices within the same technology node. The term “scaling” may also refer to adjusting (e.g., slowing down or speeding up—i.e. scaling down, or scaling up respectively) of a signal frequency relative to another parameter, for example, power supply level.
With reference to inductors, scaling reduces the distance between the inductors, causing inductive coupling between distinct VR power domains, which also leads to efficiency loss.